We fill ours 3/4 full. this is a mix of pre ground pieces and the ceramic pellets used for deburring metal parts . We use fine or med. grit pellets. The shape we use are cylinders with angle cut ends. We grind our pre forms with 120 grit diamond wheel. The first grit size we use is 220 grit.We do not use anything coarser than that for the simple reason being , WHY ?
We have already been there.
1 day / some times 2 in 220 This removes all small flats / whoopte do's
1 day in 400 grit
1 day in 600 grit
1 day in pre polish
1 day in TSP polish This is satisfactory 99% of the time
We wet and drain the stone, then place in tub while it is running.
After placing wet stone and pellets in running mach., we drizzle antibotic dish soap onto the moving stones. THE KEY WORD WAS (DRIZZLE) don't squeeze bottle as hard as you can, just enough to get a hair like stream going making 3 or 4 laps around the inside of the tub.
After about 2 minutes the rock is completly covered with soap from the tumbling action.
Now you gradually add your grit , also in a spirial motion same as the soap.
Don't pour it , lightly sprinkle it in.
At this time you will notice that the small amount of dish soap has the grit evenly coating the stone. You are not waiting for a slurry to form to carry your grit because your effectively grinding before you even replace the lid on the machine.
At this time you will probably notice that the revolving / rotating speed of the rock has slowed down.
NOW, take a spray bottle, set on spray, NOT squirt, and lightly mist the surface of the stone until the ORIGINAL speed of the moving stone has been reached.
By that I mean ,the speed it was moving at before we added anything.
Slowly misting the rock keeps the soap and grit from washing off.
Think you used too much soap? Don't worry your rocks will only get a little cleaner.
The ANTI-BACTERIAL dish soap will stop any pressure build up because the yeast type reaction from the bacteria laden rock. Rising bread dough syndrome type thing.
If you didn't use a lot more grit than necessary, there will not be a trace of it in 24 hours.
Your now ready to move on to the next grit size.
This is the procedure we use for pre forms. If starting with rough rock you will obviously need to start with 90-120 grit and rough grind until they are PLEASING TO YOUR EYE, YOUR DOING THE DRIVING.
When we are grinding rough agate we recharge every day, this removes all sludge and the grit is usually non- existant any way.
Every batch of rock will have several that are not so SMURFFY, for lack of a better word, simply throw em in the next batch and they soon will be.
The TSP Polish we get from Minnesota lapidary supply and it is the best we have found for agate and similar materials.
Their # is 1-763-631-0405 if you want to speak to a real person, or if you are shy and bashful check the on line store.
Good luck and enjoy !!!!!!